EP1914668A1 - Bildverarbeitungsverfahren und -gerät zur Verbesserung der Druckqualität in einem Punktmatrixdrucker - Google Patents

Bildverarbeitungsverfahren und -gerät zur Verbesserung der Druckqualität in einem Punktmatrixdrucker Download PDF

Info

Publication number
EP1914668A1
EP1914668A1 EP06122346A EP06122346A EP1914668A1 EP 1914668 A1 EP1914668 A1 EP 1914668A1 EP 06122346 A EP06122346 A EP 06122346A EP 06122346 A EP06122346 A EP 06122346A EP 1914668 A1 EP1914668 A1 EP 1914668A1
Authority
EP
European Patent Office
Prior art keywords
sub
image
printing
images
pixels
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP06122346A
Other languages
English (en)
French (fr)
Inventor
Rudi AGFA-GEVAERT Vanhooydonck
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Agfa NV
Original Assignee
Agfa Graphics NV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Agfa Graphics NV filed Critical Agfa Graphics NV
Priority to EP06122346A priority Critical patent/EP1914668A1/de
Priority to PCT/EP2007/060678 priority patent/WO2008046760A1/en
Publication of EP1914668A1 publication Critical patent/EP1914668A1/de
Withdrawn legal-status Critical Current

Links

Images

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/21—Ink jet for multi-colour printing
    • B41J2/2132—Print quality control characterised by dot disposition, e.g. for reducing white stripes or banding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J11/00—Devices or arrangements  of selective printing mechanisms, e.g. ink-jet printers or thermal printers, for supporting or handling copy material in sheet or web form
    • B41J11/0015—Devices or arrangements  of selective printing mechanisms, e.g. ink-jet printers or thermal printers, for supporting or handling copy material in sheet or web form for treating before, during or after printing or for uniform coating or laminating the copy material before or after printing
    • B41J11/002—Curing or drying the ink on the copy materials, e.g. by heating or irradiating
    • B41J11/0021—Curing or drying the ink on the copy materials, e.g. by heating or irradiating using irradiation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J11/00—Devices or arrangements  of selective printing mechanisms, e.g. ink-jet printers or thermal printers, for supporting or handling copy material in sheet or web form
    • B41J11/0015—Devices or arrangements  of selective printing mechanisms, e.g. ink-jet printers or thermal printers, for supporting or handling copy material in sheet or web form for treating before, during or after printing or for uniform coating or laminating the copy material before or after printing
    • B41J11/002—Curing or drying the ink on the copy materials, e.g. by heating or irradiating
    • B41J11/0021—Curing or drying the ink on the copy materials, e.g. by heating or irradiating using irradiation
    • B41J11/00214—Curing or drying the ink on the copy materials, e.g. by heating or irradiating using irradiation using UV radiation
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K15/00—Arrangements for producing a permanent visual presentation of the output data, e.g. computer output printers
    • G06K15/02—Arrangements for producing a permanent visual presentation of the output data, e.g. computer output printers using printers
    • G06K15/10—Arrangements for producing a permanent visual presentation of the output data, e.g. computer output printers using printers by matrix printers
    • G06K15/102—Arrangements for producing a permanent visual presentation of the output data, e.g. computer output printers using printers by matrix printers using ink jet print heads
    • G06K15/105—Multipass or interlaced printing
    • G06K15/107—Mask selection

Definitions

  • the present invention relates to an image processing method and system.
  • the invention relates to an image processing method and system for improving image quality in dot matrix printing systems, such as inkjet printers.
  • the invention relates to a method for improving image quality in such systems by printing mutually interstitial sub-images, for example by interlacing or interleaving such sub-images.
  • Printing a digital document is one of the most efficient ways to convey information to a user.
  • New print-on-demand technologies such as laser printing and inkjet printing enable to print documents almost instantaneously without the need for creating intermediate printing masters.
  • Inkjet printing works by jetting ink droplets through a nozzle onto a substrate.
  • a continuous stream of electrically charged ink droplets is produced and electromagnetic fields are used to guide this stream away from or towards a substrate as to form an image on said substrate.
  • a mechanical or thermal energy pulse is applied to ink residing in a small chamber in order to create a pressure wave that propels a miniscule ink droplet at high speed through the nozzle towards a substrate.
  • the pressure wave is controlled by shaping the length and the profile of the electrical waveform that is applied to the thermal or mechanical transducer in the ink chamber.
  • the volume of the droplet and the size of the ink spot are substantially fixed. In other cases the volume of the droplet can be modulated to create ink spots having different sizes on the substrate.
  • Printing the image of a document is achieved by moving the nozzle relative to the substrate along a raster by means of a shuttle in combination with a substrate transport mechanism and selectively jetting ink droplets on a substrate in response to the image of said document.
  • ink spots When the ink droplets land on a substrate, they form ink spots. Because these ink spots are small, they cannot be individually resolved by the human visual system but together they render a visual impression of the image of the printed document. Generally, a halftoning technique is used to determine the spatial distribution of ink spots that produces an optimal rendering of the image of a given document.
  • nbrNozzles inkjet nozzles are generally used that can be operated in parallel. Such an array of nozzles makes up a print head.
  • a set of parallel raster lines of pixels can be printed in one step.
  • Such a set of raster lines is called a swath.
  • the print head When a swath has been printed, the print head is moved in a slow scan direction over a distance of the length of the array of nozzles to print an additional swath of lines underneath said previous swath. This process of printing swaths is repeated until a complete document is printed on the substrate.
  • a printing pitch in the slow scan direction is often desired that is smaller than the nozzle pitch.
  • the document US 4.198.642 teaches that a value can be selected for the printing pitch in the slow scan orientation that is an integer fraction 1/n of the nozzle pitch by using an interlacing technique.
  • the document US 4,967,203 introduces a technique to resolve this problem.
  • the correlated image quality artifacts can be de-correlated.
  • the underlying assumption is that the image quality artifacts caused by variations between different nozzles are uncorrelated.
  • De-correlating the image quality artifacts diffuses them over the printed substrate so that they become less perceptible or preferably imperceptible. In many documents, this technique is referred to as shingling.
  • the method presented in US 4,967,203 uses a staggered application of ink dots such that overlapping ink dots are printed in successive passes of the print head.
  • Ink curing can be achieved by a number of mechanisms.
  • a first mechanism of ink curing is absorption of the ink into fibers of the substrate or a porous coating. This is the dominant mechanism when oil or water based inks are used.
  • a second mechanism of ink curing is coagulation of the ink by evaporation of an ink solvent.
  • pigments or dyes together with a binder material are left on the paper.
  • ink is initially absorbed by a substrate and then, depending on the vapor pressure of the solvent, evaporates in a shorter of longer time.
  • a third mechanism of ink curing is polymerization, for example under the influence of an external energy source such as a UV light source.
  • the high-energy radiation creates free radicals that initiate a polymerization reaction that solidifies the ink.
  • the main advantage of this technique is that it enables the printing on media that do not absorb ink.
  • a fourth mechanism of ink curing is phase or viscosity change by temperature. Ink is jetted at a high temperature when it is in liquid phase and solidifies when it cools down on the printed surface.
  • wet-on-wet printing is a technique wherein the droplets from different nozzles land on the same position of the substrate without intermediate curing.
  • a typical example is in color printing where up to four droplets with cyan, magenta, yellow and black ink printed by different heads mounted on the same shuttle can land on the same pixel position.
  • An advantage of wet-on-wet printing is that the final color of a pixel is not heavily affected by the order of printing the droplets because the inks physically mix before they are cured. This property is particularly advantageous in the case of bidirectional printing, because in bidirectional printing the order of printing droplets by different heads reverses when the slow scan direction reverses.
  • the piling up of droplets on the same position on the substrate also greatly increases the risk for coalescence.
  • a first solution to the problem of coalescence problem would be to reduce printing speed. By reducing printing speed more time is available to cure an ink spot before a neighboring ink spot is printed and this reduces the risk of coalescence.
  • the document WO2004/002746 describes a method and an apparatus and introduces the concept of a first "partial curing” step by a first UV source followed by "final curing” step by a second UV source.
  • the image is reconstructed by printing series of mutually interstitial images with intermediate curing.
  • the partial curing of each mutually interstitial image immediately after printing enables to control the coalescence of ink without substantially compromising the smoothness of the gloss and texture of the final printed surface.
  • the method and the apparatus in the document WO2004/002746 use only one UV lamp for the intermediate curing, they are designed for printing only in one direction along the fast scan orientation, which limits the maximum achievable printing performance compared to systems that support bidirectional printing.
  • Bidirectional printing has been described in the prior art, however not in the context of printing techniques that use intermediate curing. Many technical problems that involve the management of printing and curing, the lay out of an apparatus for such purpose, and the required image processing to suppress correlated image artifacts and to achieve a smooth and even gloss and texture of the printed result hence remain unresolved.
  • the method according to the current invention is mainly directed towards the use in dot matrix printers and specifically drop-on-demand inkjet printers, but it is not limited thereto.
  • printing as used in the invention refers to the process of creating a structured pattern of ink markings on a substrate. Non-impact printing methods are preferred but the present invention is not limited thereto.
  • the ink could be a conventional pigmented or dyed ink or colorant, but it could also be wax, a water repellent substance, an adhesive or a plastic.
  • ink is not a pure compound, but a complex mixture comprising several components such as dyes, pigments, surfactants, binders, fillers, solvents, water and dispersants, each component serving a specific function.
  • the ink could also be a material of which the viscosity or phase changes with temperature, such as wax.
  • the substrate could be paper, but it could also be textile, a synthetic foil or a metal plate.
  • printing processes include inkjet printing (drop-on-demand and continuous), thermal wax or dye transfer printing and the use of inkjet to create printing masters for offset printing.
  • a transducer, an ink chamber and a nozzle - etched in a nozzle plate - together make up a print head 122.
  • a print head 122 is mounted on a shuttle 121 that is capable to travel on a guide 120.
  • the shuttle transport is achieved by means of a belt 123, a shaft 124 and a first motor 125.
  • a substrate 101 having an ink receiving layer 102 rests on a substrate support 103 and is transported by a substrate transport mechanism comprising two rollers 110,111, a shaft 112 and a second motor 113.
  • Printing an image of a document using a printer 100 is generally achieved by moving a nozzle relative to a substrate by means of the shuttle and the substrate transport mechanisms and selectively jetting ink droplets on a substrate in response to said image of said document.
  • the orientation that corresponds with the movement of a shuttle along its guide is generally called the fast scan orientation 140.
  • the fast scan direction shall mean the direction that said shuttle moves along said fast scan orientation.
  • the orientation perpendicular to the fast scan orientation is generally called the slow scan orientation 130.
  • the slow scan direction shall mean the direction that a print head moves along said slow scan orientation relative to the substrate.
  • a raster line shall mean a virtual line on which ink droplets are printed by a nozzle along a fast scan orientation.
  • printing is preferably done bidirectionally, i.e. printing occurs in the two directions corresponding to the fast scan orientation.
  • the rectangular raster grid that is defined by the positions where a droplet can be printed is called the addressable grid 400.
  • An element of the addressable grid is a pixel 430.
  • the pixels are arranged in rows addressed by a slow scan index 450 and columns addressed by a fast scan index 460.
  • With one pixel is associated a color or a set of colorant values.
  • the color can be monochrome or full color (three color components, for example expressed as the amounts of red, green blue primaries).
  • the set of colorant values can for example be amounts or densities of cyan, magenta, yellow and black colorants.
  • the distance between two neighboring pixels on along the fast scan orientation 470 is called the fast scan pitch fastScanPitch 410, while the distance between two neighboring pixels along the slow scan direction 471 is called the slow scan pitch slowScanPitch 420.
  • the fast scan pitch fastScanPitch and the fast scan printing resolution fastScanResolution are related to each other by an inverse relationship:
  • a smaller pitch (or a higher spatial resolution) enables the rendering of finer image details and hence in general enables to achieve a higher image quality.
  • the printing resolution fastScanResolution is proportional with the firing frequency firingFrequency of the nozzles, i.e. the time rate at which ink droplets can be ejected by a nozzle.
  • the fast scan resolution fastScanResolution is dictated by the ratio of the firing frequency firingFrequency divided by the velocity fastScanVelocity in the fast scan direction:
  • an array 500 of nbrNozzles 520 inkjet nozzles can be used that operate in parallel and that produce droplets with either a fixed or a variable volume.
  • Each nozzle can be referred to by means of a nozzle index nozzleIndex that ranges from 1 to nbrNozzles.
  • the nozzle array 500 is oriented parallel to the slow scan orientation 540 although this is not a strict requirement.
  • the shortest distance between two nozzles along the slow scan orientation 540 is called the nozzle pitch nozzlePitch 510.
  • the length of the nozzle array headLength 550 is expressed as a multiple of the length of slowScanPitch.
  • a set of rows of pixels on the addressable grid that can be addressed by the nozzles of a print head during one movement along the fast scan orientation is called a swath.
  • the nozzles 630 of an array may be staggered for constructive reasons along two or more columns 660, 661.
  • the nozzle pitch 610 is defined as the shortest distance between two lines perpendicular to the slow scan orientation and going to the centers of the staggered nozzles.
  • the timing of the firing of droplets from nozzles belonging to different columns is preferably adjusted so that the pixels belonging to the same column in the image of the document also land on the same column on the printed image. By adjusting the timing this way, the processing to prepare the signals for the nozzles can be the same as if all the nozzles were virtually on the same column.
  • two staggered columns are used each having 382 nozzles.
  • the distance 611 between two nozzles in one column is 141 micrometer (1 inch/180) and the nozzle pitch 610 is 70,6 micrometer (1 inch/360).
  • the printing resolution in the slow scan orientation is increased by using one of the interlacing techniques as known in the art.
  • the resolution in the slow scan orientation can be doubled by using a slow scan interstitial factor equal to two. This brings the slow scan pitch to a value of 35,3 micrometer (1 inch/720).
  • the value of fastScanVelocity is adjusted so that value of the fast scan pitch is equal to that of the slow scan pitch.
  • not one but a set of print heads are used that print with different inks.
  • the inks have different hues but in one embodiment, they have the same hue but different densities, such as for example a light and dark cyan, or a light and dark neutral color.
  • a set of four print heads are used to print with four inks having cyan (C), magenta (M), yellow (Y) and black (K) colors.
  • these inks are curable by electromagnetic radiation such as UV light.
  • the different print heads can be mounted near or below each other, or in a staggered fashion relative to each other.
  • the values of the nozzle pitch of the different print heads are the same and the heads are mounted in such a way that the nozzles are spaced at an integer multiple of the slow scan pitch along the slow scan orientation.
  • the timing of the firing of the droplets belonging to different print heads is preferably adjusted so that they the droplets that belong to the same column in the image also land on the same column on the printed image.
  • Figure 7 also shows two optional curing sources L1 750 and L2 760. These sources are designed to boost the curing of the ink.
  • An example could be the use of a UV curable ink in combination with UV lamps that enhance polymerization of the ink.
  • Another example could be an IR source that enhances drying of the ink.
  • the output power of the sources can be controlled by the printer controller, for example by controlling the amplitude or the duty cycle of the current passing through the lamps or by controlling the number of lamps in the same source that are simultaneously powered.
  • the print heads 710, 720, 730, 740 and the curing sources 750, 760 together make up a print head assembly 700.
  • multiple curing sources L1 1750, L2 1751 and L3 1752 are used.
  • a first set of print heads 1701-1704 is provided between the sources L2 1751 and L3 1753 and between the sources L2 1751 and L3 1753 a second set of print heads 1705-1708 is provided.
  • the light sources L1 1750, L2 1751 and L3 1752 and the print heads 1701-1708 together make up a print head assembly 1700.
  • the nozzles of all the heads are shifted along a slow scan orientation 1790, 1791 axis so that nozzles belonging to different heads 1702, 1703 but having the same nozzle index print on the same raster line during the same swath.
  • the nozzles of all at least two heads 1703, 1704 are shifted along a slow scan orientation 1790, 1791 axis so that nozzles belonging to different heads 1703, 1704 but having the same nozzle index print on a different raster line during the same swath.
  • the embodiment shown in Figure 17 comprises twice the number of heads compared to the arrangement shown in Figure 7 and therefore enables to achieve faster printing speed. If printing performance needs to be further enhanced, more curing sources and more print heads can be mounted along the fast scan orientation 1780, 1781.
  • the output power of the sources is controlled by a printer controller, for example by controlling the amplitude or the duty cycle of the current passing through the lamps or by controlling the number of lamps in the same source that are simultaneously powered.
  • Figure 19 shows an embodiment featuring multiple curing stations 1950, 1951, 1952, multiple heads 1901, 1902 along a fast scan orientation 1980, 1981 and multiple heads 1901, 1919 along a slow scan orientation 1990, 1991.
  • the heads 1901, 1911 are staggered.
  • the timing of the drivers of the staggered print heads so that a single contiguous line of pixels in the halftone image that is parallel to the slow scan orientation is also printed as a single contiguous line, the staggered print heads effectively behave as one long single print head.
  • Using plural heads 1901, 1911 along a slow scan orientation increases the number of nozzles that can print simultaneously during a swath and therefore increases printing performance.
  • the multiple print heads 1801, 1811 are essentially lined up along a line 1822 parallel to the slow scan orientation 1890, 1891.
  • the print heads 1808, 1818 are mounted at a distance relative to each other so that a distance 1820 between two nozzles belonging to different heads 1808, 1818 is a multiple of the slow scan pitch 1821.
  • a disadvantage is that in the arrangement shown in Figure 18, a gap 1821 exists between the two heads 1808, 1818 where no printing occurs. This technical problem is resolved using image processing.
  • the distance 1821 between two print heads 1808, 1818 is nbrNozzles times the nozzlePitch 1821. In another embodiment of the current invention, the distance 1821 between two print heads 1808, 1818 is smaller than nbrNozzles times nozzlePitch but equal to a multiple of the nozzlePitch 1820. In the remainder of the text, the term gapSize is used to refer to the distance 1821.
  • At least one of the curing stations 1851 is split into two curing stations 1851A, 1851B.
  • printer commands are generated from a data processing system 300 such as a computer.
  • a computer comprises a network connection means 321, a central processing unit 322 and memory means 323 which are all connected through a computer bus 324.
  • the computer typically also has a computer human interface 330, 331 for inputting data and a computer human interface 340 for outputting data.
  • the computer program code is stored on a computer readable medium such as a mass storage device 326 or a portable data carrier 350 which is read by means of a portable data carrier reading means 325.
  • the fast scan motor 125, the slow scan motor 113 and the actuator of the print head 122 are controlled by a printer controller 200.
  • Printer commands 220 are received by a buffer memory 201. These printer commands contain printer controller information which is sent to a printer controller 206 and image data which is sent to an image buffer 203.
  • the printer controller controls a fast scan driver 207 that drives the fast scan motor 125 for moving the shuttle in a fast scan direction.
  • the printer controller also controls a slow scan driver 209 that drives the slow scan motor 113.
  • the controller also comprises a driver for the curing station 750,760.
  • the information in the image buffer 203 is used to drive the actuator(s) of the print head 122 by means of a print head driver 204.
  • a first step of printing the image of a document includes calculating a continuous tone raster image of said document at the printer's spatial resolution and in the printer's colorant space.
  • This process involves the transformation of a document, usually represented at the object level in one of the standardized formats such as PDF®, MS-Word®, or PostScript ®, into a continuous tone raster image.
  • Such a continuous tone raster image contains for every addressable position of the printer grid a pixel value representing on a near-continuous tone scale the amount of ink that belongs to that pixel position.
  • the calculations are done on a computer system 300 by means of a computer program such as "Adobe PostScript Printer Driver” commercialized by the company Adobe Systems Incorporated, located in San Jose CA.
  • a second step comprises sub-sampling said continuous tone image.
  • Every square 801 corresponds with a pixel at the full printer resolution.
  • the fast scan pitch fastScanPitch 810 and slow scan pitch slowScanPitch 820 are in this particular example are identical.
  • the sub-sampling consists of retaining pixel values only at the positions indicated with an x-mark 802.
  • the pixels in the resulting sub-sampled image are spatially laid out on a grid that in this case is 45 degrees rotated with regard to the addressable grid of the printer and form a checkerboard pattern and that contains half of the pixels as the original image.
  • the positions 802 of the pixels in the sub-sampled image are defined by first identifying two diagonal orientations that correspond with the diagonal lines of any rectangular cell 830 on the addressable grid 800 that contains the same number of pixels NP (NP>1) in the fast and slow scan orientations.
  • the orientations of said two diagonal lines are referred to as a first diagonal orientation 831 and a second diagonal orientation 832.
  • Said sub-sampled image is then defined as the set of one out of every two pixels 801 on every row 850 of the addressable printer grid 800, arranged in such a way that they form contiguous series 880, 881 of pixels 802 along said two diagonal orientations 831,832.
  • sub-sampling is performed by simply selecting the pixel values in the continuous tone raster image that correspond with the position of pixels in the sub-sampled image.
  • first a low pass filter is applied on the continuous tone raster image, after which the pixel values are selected in said filtered image that correspond with the positions in the sub-sampled image.
  • a third, digital halftoning step is required according to said preferred embodiment.
  • the pixels in the continuous tone raster image or the sub-sampled image may be represented with 8 bits per colorant component, while the printer many only be able to print four distinct tone levels represented by 2 bits per colorant component.
  • the task of the digital halftoning step is spatially diffusing the image artifacts that result from the quantization of the pixels from eight to two bits per color component.
  • the result of halftoning a sub-sampled continuous tone raster image is a halftoned sub-sampled image.
  • Digital halftoning techniques have been known to the person skilled in the art. Examples include error diffusion or a threshold mask based frequency modulation techniques.
  • the steps of calculating a continuous tone raster image of said document, sub-sampling said image and halftoning said sub-sampled image can be optimized for performance and memory usage.
  • the continuous tone raster image is first calculated at half the printer resolution in the fast scan orientation and at the full printer resolution in the slow scan orientation.
  • Figure 9 shows that the pitch 910 of the continuous tone raster image in the fast scan direction is two times larger than the pitch 810 of the addressable grid of the printer.
  • This continuous tone image can be halftoned using one of the techniques known by the person skilled in the art such as error diffusion or a threshold mask based frequency modulation technique.
  • the pixels of the halftoned image are mapped to the pixels of the addressable grid of the printer at the positions indicated with an x-mark in Figure 9.
  • This mapping is achieved by using the following rule set that maps a pixel of the halftoned image having row index [i] and column index [j] onto a pixel of the addressable printer grid having row index [k] and column index [1]:
  • the halftoned image is separated into mutually interstitial sub-images.
  • the halftoned sub-sampled image is separated into a primary set of M (M>1) mutually interstitial sub-images along a first diagonal orientation.
  • Figure 11A shows the addressable pixel 1103 grid of the printer having a fast scan pitch 1101 and slow scan pitch 1102.
  • the positions of the halftoned pixels of the sub-sampled image are indicated by a black dot 1104.
  • the figure also shows a first 831 and a second 832 diagonal orientation.
  • Separating an original image into mutually interstitial sub-images shall mean that every pixel as a whole (including all of its color components) in the original image 1100 is selectively assigned to one of several sub-images having the same size and resolution as the original image in a way that, when said sub-images are added together, the original image is reconstructed.
  • Separating an image into sub-images along an orientation shall mean that a set 880, 881 of subsequent pixels 802 in an original image that lie on a line that is parallel to said orientation 831, 832 shall be assigned to the same sub-image.
  • step 4 The effect of the combining the first and the second sub-steps of step 4 is that a total of M*N sub-images are obtained. These sub-images can be indexed by means of a two-dimensional index [i,j].
  • the second sub-step can be skipped.
  • FIG. 10 A preferred embodiment of the current invention is shown in Figure 10 wherein M equals two and N equals two.
  • the halftoned sub-sampled image is separated into four sub-images with indices [1,1], [1,2], [2,1] and [2,2].
  • the order of the printing of the sub images is organized in such a way that:
  • the pixels belonging to different sub-images are printed during subsequent passes of the print head assembly, time is available for curing the pixels belonging to a first sub-image, before pixels of a subsequent sub-image are printed. This enables also to reduce the risk of coalescence between droplets of pixels belonging to different sub-images.
  • a forced intermediate curing step by means of an energy source is performed between the printing of sub-images to further suppress ink coalescence between droplets of pixels belonging to different sub-images.
  • Intermediate curing shall mean the curing of a sub-image just after it has been printed.
  • a forced intermediate curing step by means of an energy source is performed between the printing of sub-images to further suppress ink coalescence between droplets of pixels belonging to different sub-images.
  • Intermediate curing shall mean the curing of a sub-image just after it has been printed.
  • intermediate curing is achieved by powering a first curing source 750.
  • a final curing of partially cured dots that were printed in a prior swath is achieved by powering a second curing source 760.
  • intermediate curing is achieved by powering a second curing source 760.
  • a final curing of partially cured dots that were printed in a prior swath is achieved by powering a second curing source 750.
  • Figure 17 illustrates of a second embodiment of the current invention.
  • the following explanation concentrates on the printing of the image using the print heads 1701, 1705 with cyan ink, although the printing of the image with print heads containing other inks is entirely analogue.
  • the order of the printing of the sub-images is organized in such a way that:
  • pixels on a line belonging to two or more different sub-images 1021, 1022 are printed in one single pass, but by different print heads 1701, 1705.
  • said sub-images belonging to said secondary set of sub-images printed in said single pass are derived from the same sub-image belonging to said primary set of sub-images.
  • the sub-images 1011, 1012 belonging to said secondary set of sub-images are derived form the same sub-image 1010 from said primary set of sub-images.
  • FIG. 19 A variation of the embodiment shown in Figure 17 is shown in Figure 19.
  • a group of staggered print heads 1901, 1911 that act and behave as one single print head replaces a single print head 1701.
  • the increased number of nozzles of a group of staggered print heads enables to print at faster speeds.
  • intermediate curing of dots printed by at least one head 1705-1708 is achieved by powering a first curing source 1751 and intermediate curing of dots printed by at least one head 1701-1704 is achieved by powering a second curing source 1750.
  • a final curing of partially cured dots that were printed in a prior swath is achieved by powering a third curing source 1752.
  • intermediate curing of dots printed by at least one head 1701-1704 is achieved by powering said second curing source 1751 and intermediate curing of dots printed by at least one head 1705-1708 is achieved by powering said third curing source 1752.
  • a final curing of partially cured dots that were printed in a prior swath is achieved by powering said first curing source 1750.
  • Figure 12 demonstrates a preferred embodiment to implement the invention according to a first embodiment.
  • the pixels belonging to the different sub-images are indicated as follows:
  • the printing process works according to the following steps.
  • a step 1 the position headPosition of the print head is set at 0 and a first swath is printed that prints sub-image [1,1].
  • a first diagonal pattern 1210 originates.
  • a rhombus like pattern 1211 originates consisting of "missing pixels" of sub-image [2,2] (indicated by the circle around "4" surrounded by printed pixels from sub-images [1,1], [1,2] and [2,1]
  • a second diagonal pattern 1213 originates between pixels belonging to sub-image [1,1] and sub-image [2,2]. From here on the steps 2, 3 and 4 are repeated until the complete image is printed.
  • the swaths 1 and 3 are printed along a first fast scan orientation and the swaths 2 and 4 along the opposite fast scan orientation.
  • the orientation of the diagonal pixel structures 1210 and 1213 alternates during the printing and this, for example in combination with an intermediate curing step, may give rise to a form of banding that is correlated with the orientation of the diagonal structures.
  • the above mentioned form of banding can be avoided by requiring that on any group of N consecutive lines of the addressable printer grid all the pixels belonging to a sub-image derived from a first primary sub-image are printed before the printing starts of pixels belonging to a sub-image derived from a another primary sub-image.
  • the pixels of a sub-image [1,1] and sub-image [1,2] derived from the same primary sub-image [1] are printed in two swaths 1301 and 1302 on the lines 0 to 21.
  • the pixels of the sub-image [2,1] and sub-image [2,2] derived from a primary sub-image [2] are printed in two swaths 1303 and 1304 on the lines 0 to 17.
  • the pixels derived from a first primary sub-image [1] are printed before the pixels derived from a second primary sub-image [2].
  • the method proceeds by printing the swaths 1305 and 1306 to print pixels derived from primary sub-image [1] on the lines 22-43 and by printing (not shown on Figure 13) swaths to print pixels derived from a second primary sub-image [2] on lines 18 to 40.
  • the method achieves that on any group of lines, the pixels derived from a first primary sub-image are printed before the pixels derived from a second primary sub-image.
  • the method also retains the original objective of the de-correlating image quality artifacts by having pixels on the same line printed by different nozzles.
  • the order of the swaths that print pixels derived from the same primary sub-image is reversed.
  • the order of the swaths 1303 and 1304 may be reversed.
  • the grid on which pixels that belong to a primary sub-images are positioned is not defined by diagonal lines, as in Figure 8, but on a rectangular grid.
  • An example of this is easily devised by shifting in Figure 13 the pixels on the lines having odd row numbers over one fast scan pitch fastScanPitch 1341 to the left. By doing this, pixels of the four sub images are organized on a rectangular grid of rows and columns.
  • this problem is resolved by including after each slow scan step according to one of the prior embodiments an additional slow scan step ASSS.
  • Figure 20 shows a case in which two heads 2001, 2002 together form a print head sub-assembly 2000.
  • Moving the print head assembly 2000 in an additional slow scan step over a distance 2013 enables to print those lines in the image that could not printed in a previous position of said print head, because they were in between the nozzles of the print head 2001 and the print head 2002.
  • Figure 21 shows a case in which: gapSize ⁇ nbrNozzles * nozzlePitch ;
  • a nozzle redundancy problem originates, because certain lines can be printed by nozzles belonging to said print head both before and after said additional slow scan step.
  • the nozzles of print head 2101 surrounded by a dotted box 2130 in Figure 21 print after the additional slow scan step over a distance 2113 on the same lines as the nozzles of said print head 2101 surrounded by a dotted box 2131 before said slow scan step over a distance 2113.
  • the nozzle redundancy problem can be solved in three ways:
  • the nozzles of a print head that correspond with common line positions are switched off when the print head is in a position before an additional slow scan step.
  • the lines on the common line positions in that case are printed by nozzles after an additional slow scan step.
  • the second method is essentially the complement of the first method.
  • the nozzles of a print head that correspond with common line positions are switched off when the print head is in a position after an additional slow scan step.
  • the lines on the common line positions in that case are printed by nozzles before an additional slow scan step.
  • a pixel on a common line is alternately printed by a nozzle of a print head before and after an additional slow scan step.
  • This third method has the advantage that pixels on the same line are printed by two different nozzles and that image quality artifacts that are related with a specific nozzle are spatially diffused.
  • a swath 1411 prints pixels of sub-image [1,1] on the lines 0 to 8 and the lines 20 to 28. This is followed by a additional slow scan step of 10*SSPitch and a second swath 1412 to print pixels of the same sub-image [1,1] on the lines 10 to 18 and 30 to 38.
  • the result of the swaths 1411 and 1412 is that pixels of the first sub-image are printed on the even lines having row numbers from 0 to 38.
  • the method proceeds by printing pixels of sub-image [1,2] in swaths 1413 and 1414 on the lines having odd row numbers 1 to 39. At that point all the pixels of the primary sub-image [1] on the lines having row numbers 0 to 40 are printed.
  • the pixels of the primary sub-image [2] are printed in a sequence of swaths 1415, 1416, 1417, 1418 on the lines having row numbers 0 to 35.
  • the slow scan steps are selected such that on any line or group of lines the pixels of the primary sub-image [1] are printed before the pixels of the primary sub-image [2].
  • the order of printing swaths of pixels that belong to the same primary sub-image is permutated.
  • the order of the swaths 1411, 1412, 1413 and 1414 is permutated.
  • Figure 7 shows an arrangement for intermediate curing comprising two curing stations and Figure 17 shows an arrangement for intermediate curing comprising three curing stations. According to the principles of the current invention even more curing stations may be used to print multiple sub-images during pass of the print head assembly.
  • the current invention is preferably used for printing applications that are typically handled by a silk printing process, but is not limited to such applications.
  • the addressable grid of the printer is a rectangular addressable grid of which only half the pixels are addressed. It should be clear to the person skilled in the art that this is equivalent to a printer that has a native addressable grid with pixels arranged in a checkerboard pattern.
  • Also part of the invention is the apparatus that uses any of the methods according to the current invention and that has the technical features as set out above.
  • Also part of the invention is a computer program that performs the steps according the current invention.

Landscapes

  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Engineering & Computer Science (AREA)
  • Quality & Reliability (AREA)
  • Physics & Mathematics (AREA)
  • Mathematical Physics (AREA)
  • General Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Ink Jet (AREA)
EP06122346A 2006-10-16 2006-10-16 Bildverarbeitungsverfahren und -gerät zur Verbesserung der Druckqualität in einem Punktmatrixdrucker Withdrawn EP1914668A1 (de)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP06122346A EP1914668A1 (de) 2006-10-16 2006-10-16 Bildverarbeitungsverfahren und -gerät zur Verbesserung der Druckqualität in einem Punktmatrixdrucker
PCT/EP2007/060678 WO2008046760A1 (en) 2006-10-16 2007-10-09 Image processing method and apparatus for improving image quality in dot matrix printer

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP06122346A EP1914668A1 (de) 2006-10-16 2006-10-16 Bildverarbeitungsverfahren und -gerät zur Verbesserung der Druckqualität in einem Punktmatrixdrucker

Publications (1)

Publication Number Publication Date
EP1914668A1 true EP1914668A1 (de) 2008-04-23

Family

ID=37607064

Family Applications (1)

Application Number Title Priority Date Filing Date
EP06122346A Withdrawn EP1914668A1 (de) 2006-10-16 2006-10-16 Bildverarbeitungsverfahren und -gerät zur Verbesserung der Druckqualität in einem Punktmatrixdrucker

Country Status (1)

Country Link
EP (1) EP1914668A1 (de)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014164166A1 (en) * 2013-03-11 2014-10-09 Eastman Kodak Company Printhead including coanda catcher with grooved radius
EP2848421A1 (de) 2013-09-12 2015-03-18 Agfa Graphics Nv Objekttintenstrahldruck auf großen quaderförmigen Körpern
EP3017943A1 (de) 2014-11-06 2016-05-11 Agfa Graphics Nv Nachhaltige lithografische Druckplatte
EP3017945A1 (de) 2014-11-06 2016-05-11 Agfa Graphics Nv Tintenstrahl-CTP-Verfahren zur Herstellung eines Satzes von lithographischen Druckplatten
CN106061744A (zh) * 2014-03-05 2016-10-26 爱克发印艺公司 带有液体散布网孔的喷墨维护设备
EP3392049A1 (de) 2014-01-21 2018-10-24 Agfa Nv Förderband für eine tintenstrahldruckvorrichtung

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4198642A (en) 1978-01-09 1980-04-15 The Mead Corporation Ink jet printer having interlaced print scheme
US4748453A (en) * 1987-07-21 1988-05-31 Xerox Corporation Spot deposition for liquid ink printing
US4967203A (en) 1989-09-29 1990-10-30 Hewlett-Packard Company Interlace printing process
US6092890A (en) 1997-09-19 2000-07-25 Eastman Kodak Company Producing durable ink images
US6437883B1 (en) * 1998-06-26 2002-08-20 Canon Kabushiki Kaisha Facsimile apparatus and print control method
WO2004002746A1 (en) 2002-07-01 2004-01-08 Inca Digital Printers Limited Printing with ink
US6679583B2 (en) 2001-10-31 2004-01-20 Agfa-Gevaert Fast mutually interstitial printing

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4198642A (en) 1978-01-09 1980-04-15 The Mead Corporation Ink jet printer having interlaced print scheme
US4748453A (en) * 1987-07-21 1988-05-31 Xerox Corporation Spot deposition for liquid ink printing
US4967203A (en) 1989-09-29 1990-10-30 Hewlett-Packard Company Interlace printing process
US6092890A (en) 1997-09-19 2000-07-25 Eastman Kodak Company Producing durable ink images
US6437883B1 (en) * 1998-06-26 2002-08-20 Canon Kabushiki Kaisha Facsimile apparatus and print control method
US6679583B2 (en) 2001-10-31 2004-01-20 Agfa-Gevaert Fast mutually interstitial printing
WO2004002746A1 (en) 2002-07-01 2004-01-08 Inca Digital Printers Limited Printing with ink

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014164166A1 (en) * 2013-03-11 2014-10-09 Eastman Kodak Company Printhead including coanda catcher with grooved radius
EP2848421A1 (de) 2013-09-12 2015-03-18 Agfa Graphics Nv Objekttintenstrahldruck auf großen quaderförmigen Körpern
EP3392049A1 (de) 2014-01-21 2018-10-24 Agfa Nv Förderband für eine tintenstrahldruckvorrichtung
CN106061744A (zh) * 2014-03-05 2016-10-26 爱克发印艺公司 带有液体散布网孔的喷墨维护设备
CN106061744B (zh) * 2014-03-05 2018-03-27 爱克发有限公司 带有液体散布网孔的喷墨维护设备
EP3017943A1 (de) 2014-11-06 2016-05-11 Agfa Graphics Nv Nachhaltige lithografische Druckplatte
EP3017945A1 (de) 2014-11-06 2016-05-11 Agfa Graphics Nv Tintenstrahl-CTP-Verfahren zur Herstellung eines Satzes von lithographischen Druckplatten

Similar Documents

Publication Publication Date Title
US8018634B2 (en) Image printing method and system for improving image quality in dot matrix printer
US20080192266A1 (en) Image Processing Method and Apparatus For Improving Image Quality in Dot Matrix Printer
EP1732306B1 (de) Bildverarbeitungsmethode zur Verringerung von Bildstörungen
US6254217B1 (en) Apparatus and method for hue shift compensation in a bidirectional printer
US6980328B2 (en) Direction-dependent color conversion in bidirectional printing
EP0633139B1 (de) Verschachteltes Druckverfahren
JPH0531920A (ja) インクジエツト記録装置
US6663222B2 (en) Ink jet printer with nozzle arrays that are moveable with respect to each other
JPH03231861A (ja) インクジェットプリント方法及び装置
EP1914668A1 (de) Bildverarbeitungsverfahren und -gerät zur Verbesserung der Druckqualität in einem Punktmatrixdrucker
US10286679B2 (en) Printing apparatus and printing method
EP0628415A2 (de) Wiedergabetreue Aufzeichnungsbetriebsarten
JP2017109365A (ja) 印刷装置及び印刷方法
KR100654203B1 (ko) 잉크젯 기록 장치 및 잉크젯 기록 방법
US9579884B2 (en) Image formation apparatus and image formation method
EP1930169A1 (de) Härtungsverfahren für Tintenstrahldruckvorrichtung
WO2008046760A1 (en) Image processing method and apparatus for improving image quality in dot matrix printer
JP2012206314A (ja) インクジェット記録装置およびインクジェット記録方法
WO2008068211A1 (en) Curing method for inkjet printing apparatus
CN110091606B (zh) 印刷装置和印刷方法
US6523939B1 (en) Choosing print passes and speed based on required number of drops for each swath
JP2002210937A (ja) 相互に動き得るノズルアレイを有するインキジェットプリンター
JPH08127138A (ja) インクジェット記録装置
EP1216838B1 (de) Tintenstrahldrucker mit relativ zueinander beweglichen Düsenreihen

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IS IT LI LT LU LV MC NL PL PT RO SE SI SK TR

AX Request for extension of the european patent

Extension state: AL BA HR MK RS

AKX Designation fees paid
REG Reference to a national code

Ref country code: DE

Ref legal event code: 8566

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

18D Application deemed to be withdrawn

Effective date: 20081024